Quick-release switch with forced opening with improved mounting tolerance

ABSTRACT

To improve the possibilities of using a fast-action switch with positive opening, of the end-of-travel type, the switch is equipped with a set of compression springs which cause its moving equipment to rock and with a set of compensating springs which allow its operating plunger to move through an additional travel after switching, without damaging interference with a positive opening paddle. The additional travel is increased by placing the compensating springs between a front conducting element and the moving equipment which rocks at the time of switching.

BACKGROUND OF THE OF THE INVENTION

1. Field of the Invention

A subject of the present invention is a fast-action make-and-breakswitch. Fast-action make-and-break switches are switches in which thecurrent is cut quickly, as opposed to switches in which the separationof electrical contacts is slow and depends on the speed of manual actionof an operator. The switch of the invention is more particularly aswitch of the end-of-travel type, for which the fitting and thereforeusage tolerances are improved. What happens is that, according to theinvention, the user has available to him, for an end-of-travel switch ofsmall size, a greater tolerance between a positive opening position(POP) and an end-of-travel position (PFC). The distance separating thesetwo positions can therefore be best used by the user to stop a movingbody more easily or to absorb its spread out which has traveled beyondthe position POP.

2. Discussion of the Background

A fast-action make-and-break switch that can be used as an end-of-travelswitch is known, particularly from French patent, FR-A-2 579 009. Theuse of these switches is subject to standardized constraints. Inparticular, in addition to having a fast-action make-and-breakmechanism, these switches have to be fitted with a positive openingmechanism to avoid defective operation of the switch when actuated as aresult of a contact that has to be disconnected becoming stuck. Theprinciple is as follows. For action exerted on an operating plunger, atthe start, moving equipment internal to the switch disconnects contactswhich are normally closed (known as normally closed contacts).Thereafter, the fact of continuing to depress the plunger causes achange in state of a lever tasked with separating a conducting elementfrom contacts on which it was resting, if this separation could notoccur beforehand. This positive opening has to be capable of detachingthe conducting element from the contacts. The “sticking” concerned isthat which may have resulted from welding through the passage of a(standardized) short-circuit current of one thousand amperes. What thismeans is that the rocking mechanism and the lever are very robust inorder to perform this unsticking. Under normal circumstances, of course,such unsticking is not needed because the switch will have performed theexpected fast-action breaking.

Under normal circumstances, after the expected breaking, the rocking ofthe lever of the positive opening mechanism tends to bring the lattercloser to the normally closed moving conducting element which has beenseparated. This mechanism has a detrimental consequence. While havingits usefulness, it does nonetheless restrict the possibility ofcontinuing to depress the plunger after the lever has come into contactwith the conducting element that it has to separate, in addition to thenatural separation. What happens is that, if action continues to beexerted on the plunger, the moving equipment becomes crushed and damageis therefore done to the end-of-travel switch.

With a view to obtaining a greater distance between the opening of thecontacts for electrical isolation purposes, the aforementioned Frenchpatent envisions associating a conducting element with the movingequipment via a set of compensating springs. By taking this approach,the force exerted by the lever would be in a direction in which themoving equipment would tolerate deformation. This being the case, thetolerance on fitting adjustment between a positive opening point POP andan end-of-travel limit PFC is extended typically from a value of 0.5 mmto 1 mm. In other words, with this mechanism, the fitting tolerance orrange of use of the fast-action end-of-travel switch is markedlyimproved.

However, it remains the case that, for a total travel of 5 mm, thedepression distance separating a point of action PA, in which the movingequipment rocks, from the positive opening point POP is still great, andof the order of 2 mm. This means that, with such a mechanism, normalinitiated opening will occur for a given position PA, whereas positiveopening will not occur until the plunger has been pushed in 2 mmfurther. This difference is annoying to a user. What the user actuallywants is, for normal operation or positive operation (and in this caseeven with slow opening), for the opening of the contact to occur for oneand the same depressed position of the switch plunger. Alternatively, ifthis is not possible, he wants opening to occur at positions which aretruly very close together. In practice, in the invention, it will beshown that a precision of the order of 1 mm can be obtained, which isfar better than the previous 2 mm.

SUMMARY OF THE INVENTION

In order to overcome this problem, the solution of the inventionconsists in causing the positive opening action, and the deformation ofthe moving equipment, to be exerted on one and the same conductingelement, the normally closed conducting element, the one at the front ofthis moving equipment. It will actually be shown that, for the sameoverall switch size, a greater tolerance can be achieved using theinvention. The distance separating the positive opening point from theend-of-travel position will be greater with the invention than in thecited prior art.

A subject of the invention is therefore a fast-action make-and-breakswitch comprising

a casing fitted with four electrical contacts, facing each other inpairs,

inside this casing, moving equipment carrying along, at each end of itsmovement, a rear conducting element and a front conducting element,these elements being brought respectively and alternately into contactwith two first or two second corresponding opposing contacts,

a set of compression springs resting against this moving equipment andagainst one end of a plunger for operating the switch,

a rocking control connected mechanically to the plunger and capable ofexerting positive action on the front conducting element when theplunger is in a pushed forward position,

a set of compensating springs inserted between the moving equipment andone contact element,

a housing in a plane of the moving equipment to accommodate the set ofcompensating springs,

characterized in that

this housing is located on the same side as the front conductingelement.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood upon reading the descriptionwhich follows and from examining the accompanying figures. These aregiven merely by way of nonlimiting indication of the invention. Thefigures show:

FIGS. 1a to 1 f: schematic depictions of the fast-action make-and-breakswitch of the invention in various positions of operation and itscomparison with a depiction of the same type for the prior art;

FIG. 2: a diagram showing the various tolerances afforded by the devicesof the prior art and, by way of comparison, by the device of theinvention;

FIG. 3: a schematic depiction of the rocking action used to positivelyopen the switch of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1a to 1 e show various states of the fast-opening make-and-breakswitch of the invention. This switch comprises, in a casing 1 depictedschematically, four electrical contacts 2 to 5. These contacts face eachother in pairs. In particular, the contact 2 faces the contact 3 and thecontact 4 faces the contact 5. These contacts are connected toelectrical connections, not depicted. These electrical connections areintended to carry electrical potential according to whether the switchis closed or open. The contacts 2 to 5 comprise, in order to makeelectrical contact, studs such as 6, possibly covered with a layer ofsilver or some other material capable of improving the electricalcontact and not likely to give rise to deposits if electrical arcs arestruck.

Moving equipment 4 is located in the casing 1. This moving equipmentcarries along conducting elements at each end of a movement depicted bythe double-headed arrow 8. A first, front, conducting element 9 islocated at the opposite end to one end 10 of a plunger 11 via which theswitch of the invention is operated. The plunger 11 is used inparticular as a plunger of the end-of-travel type. A rear conductingelement 12 is placed securely in the moving equipment, on the other sidethereof with respect to the front conducting element 9. The elements 9and 12 are used to make electrical connections between the contacts 4and 5 and 2 and 3, respectively.

A set of two compression springs 13 and 14 rests, on the one hand, onthe moving equipment 7 and, on the other hand, on another end 15 of theplunger 11. The springs 13 and 14 are in compression. They are orientedas the two sides of an isosceles triangle, the height of which is in thedirection of the plunger 11.

The switch also comprises a rocking control which will be looked at ingreater detail when examining FIG. 3, but the effect of which can besymbolized by the action of a stop 16 on the front conducting element 9.The rocking control is such that the stop 16 moves toward the element 9when the plunger 11 penetrates the casing 1. Penetration of the plunger11 is by pushing on this plunger.

The moving equipment also comprises a housing 17 to accommodate a set ofcompensating springs 18 and 19. In practice, the moving equipment 7comprises, for this housing 17, a cavity 20 surmounted by the frontconducting element 9. The element 9 is held in the cavity 20 by thesprings 18 and 19 on the one hand, which rest on this element 9 and onthe bottoms 21 and 22 of the cavity, and, on the other hand, by thepresence of turned-in rims 23 and 24. The rims 23 and 24 are turned inover the cavity 20 and retain the element 9.

According to an essential feature of the invention, the housing 17 madein the cavity 20 is located on the same side as the front conductingelement 9 rather than, as it was in the prior art, on the same side asthe rear conducting element 12.

From examining the positions of the switch in FIGS. 1a to 1 e, theimprovement afforded by the invention over an equivalent embodiment ofthe prior art, FIG. 1f, will be better understood. The figures presentedare entitled, respectively, PRP, position at rest, PA−, position ofaction just before the fast action, PA+, position of action just afterthe fast action, POP, positive opening position, PFC, end-of-travelposition, and PRP, a state comparable with that of FIG. 1a but for anembodiment of the prior art.

In FIG. 1a, PRP, the stop 16 is away from the element 9 and the end 10of the plunger 11 is deployed to its maximum extent. In the positionPA−, the plunger is depressed to just before a position of equilibrium,just before fast-action breaking. In the latter instance, the twosprings 13 and 14 are almost aligned with one another. They compress.Through a judicious choice of spring weights, the component oriented inthe direction of the arrow 8 of the resultant of the reaction exerted bythe compression springs 13 and 14 is weaker than the resultant forceexerted by the compensating springs 18 and 19, this being the casethroughout the travel from PRP to PFC. This being the case, between theposition PRP and the position PA− the moving equipment 7 does not move.Above all, the springs 13 and 14, by compressing, change orientation andallow the end 15 of the plunger 11 to penetrate toward the center of themoving equipment 7. FIG. 1a shows a distance E, known as the shorttravel or approach travel, which corresponds to the depression of theplunger from the position PRP to the position PA−. This distance E, forall practical purposes, is generally of the order of 2 mm. It isnecessary for correct operation of the end-of-travel switch throughoutits life (differential travel, tolerances, internal wear, etc.)

In FIG. 1c, position PA+, a very small movement of the plunger 11, has,by the effect of relaxing the compression spring 13 and 14, caused themoving equipment 7 to move quickly with respect to the end 15. Thelatter can be considered as not having moved from the position of FIG.1b to that of FIG. 1c. This being the case, in normal operation, thefront conducting element 9 is separated quickly from the contacts 4 and5 while the rear element 12 comes into contact with the contacts 2 and3. At this stage, if there had not been further constraints,particularly those imposed by the standard, this operation could havebeen deemed to be satisfactory.

In the position PA+, the springs 13 and 14 tend to return the plunger 11toward the front element 9. Either an additional spring stronger thanthe resultant of the springs 13 and 14 and exerting a force in theopposite direction, but not depicted, then rests on the casing 1 and onthe plunger 11 in order to redeploy it or, in the position PA+, thesprings 13 and 14 are at rest. For the switch to be reversible, theformer solution is adopted.

By contrast, in FIG. 1d, it is shown that if the plunger 11 continues tobe depressed, this plunger approaches a position known as POP in whichthe stop 16 comes into contact with the conducting element 9 if thelatter has remained stuck to the contacts 4 and 5. If the switch isoperated normally, in the position POP, the stop 16 does not come intocontact with the conducting element 9. By contrast, if the conductingelement has remained stuck in the position POP, it comes into contactwith it. Furthermore, it is possible, for the position POP, to adopt notthe position in which the stop 16 comes into contact with the element 9but rather a position in which separation of the contact is guaranteed.This position is embodied by the end 25 of the stop 16.

FIG. 1e shows the end-of-travel position in which the plunger 11 hasbeen depressed a little further, by a distance 26 compared with itsposition in FIG. 1d. The distance 26 represents the long additionaltravel for positive opening. It is represented by the movement of theend 15. At the same time as the end 15 moves by the additional travel26, the stop 16 moves by an interference distance 27. It will be seenlater on why the distance 27 is not equal to the distance 26 while atthe same time being mechanically linked thereto.

In this type of operation, the result is that the moving equipment 7has, in order to contain the compression springs 13 and 14 in theirposition corresponding to FIG. 1a and in their position corresponding toFIG. 1e, to have the shape of an asymmetric lozenge. The asymmetry stemsfrom the benefit of having the position PA closer to the position PRPthan to the position PFC in all switches. This makes use thereof easier.This asymmetric lozenge shape is to be understood as meaning animperfect lozenge of which part, in this instance the part located onthe same side as the front conducting element 9, is closed at a moreacute angle than the part which closes on the same side as theconducting element 12. As a result of this, the cavity 20 may have aU-shape, in which the branches of the U can be far deeper than would bethe case if this cavity had been formed on the side where the angle atwhich the lozenge closes is more obtuse. The branches of the U embracethe pointed corner of the asymmetric lozenge formed by a cavity 28 ofthe moving equipment 7 in which the springs 13 and 14 move. In FIG. 1eit can be seen that the asymmetry results from the accentuatedinclination of the springs 13 and 14 as a result of the additionaldepression of the plunger 11.

By contrast, FIG. 1f shows a comparison of what occurs in the prior art.For the same movement of the front and rear conducting elements 9 and12, with the same asymmetric shape of the lozenge-shaped cavity 28 ofthe moving equipment 7, the overall size of the switch has to be longer(in the direction of thrust of the plunger 11). If it were not longer,the additional travel 26 and the additional travel 27 would have to bereduced. So, for a given embodiment with given compression andcompensating springs and with a given size of cavity 28 (which remainsshaped as an asymmetric lozenge), the distance 26 can be greater withthe invention.

FIG. 2 shows, as a comparison, the position of the end 15 in thepositions PRP, PA, POP and PFC in the prior art, in the improvement madein the aforementioned patent and according to the invention. In theprior art, the short initial travel, or approach travel, is of the orderof 2 mm whereas the total travel is normally of the order of 5 mm.Without the improvement afforded by the compensating springs, theresidual guaranteed positive opening travel CRA+ is of the order of 0.5mm. In practice, the distance separating the positions PA and POP waspreviously linked only to tolerances on the manufacture of the switches.With the presence of the compensating springs mounted as per theaforementioned patent, the position POP can be brought about 0.5 mmcloser to the position PA. According to the invention, the bottom linein FIG. 2, the position POP will be brought 1.5 mm closer so that theremaining distance between the position PA and the new position POP isnow merely of the order of 1 mm.

FIG. 3 shows, on the plunger 11, the end 10, the end 15 which drives thesprings 13 and 14 and an operating end 29 which operates the stop 16.The stop 16, also known as a paddle, essentially has an axis of rotation30 which here is perpendicular to the plane of FIG. 3 and to theelongate direction of the plunger 11. At the instant when the positiveopening action occurs, the end 29 presses via a bearing point 31 on thepaddle 16. This pressure is exerted with an operating radius 32. At thissame instant, an end 33 of the paddle comes into contact with the frontconducting element 9 (if it is stuck) . The operating radius of actionat the end 33 is the radius 34 whose value is, to start with, greaterthan the radius 32. This being the case, there will be a large forwardmovement at the end 33 for a short forward movement at the end 29. Bycontrast, toward the end of the thrust, the paddle 16 has rocked. Theend 33 has a working radius for pressing on the element 9 which is lowerin value than the radius 34. By contrast, the radius 32 increases. Theconsequence of this is that toward the end of the travel, the additionaltravel 26 of the plunger 11 will be greater than the additional travel27 of the front conducting element 9.

FIG. 3 again shows part of the casing 1 and, schematically, a compressedadditional spring 35 tending to cause the plunger 11 to deploy. Thedistance PRP-PFC in practice corresponds to the deflection of the spring35.

The end result of the invention is that, although the additional travel27 can be greater than it was in the prior art, by virtue mainly of theasymmetry, the additional travel 26 will also of course be greater.Furthermore, as indicated hereinabove, the positive opening point POPwill be brought very close to the point of action PA. The inventiontherefore presents the user with the advantage of a longer guaranteedpositive opening additional travel CRA+ without any increase in the sizeof the end-of-travel switch.

What is claimed is:
 1. A fast-action make-and-break switch comprising: acasing fitted with a first pair of electrical contacts and a second pairof electrical contacts, said first pair of electrical contacts facingsaid second pair of electrical contacts; moving equipment disposedinside said casing and carrying along at each end of a movement a rearconducting element and a front conducting element, said rear conductingelement being brought alternately into contact with each of said firstpair of electrical contacts, and said front conducting element beingbrought alternatively into contact with each of said second pair ofelectrical contacts; a set of compression springs resting against themoving equipment and against one end of a plunger for operating theswitch; a rocking control connected mechanically to the plunger andconfigured to exert positive action on the front conducting element whenthe plunger is in a pushed forward position; a set of compensatingsprings inserted between the moving equipment and one of the front andrear conducting elements; and a housing in a plane of the movingequipment to accommodate the set of compensating springs; wherein thehousing is located on a same side as the front conducting element. 2.The switch as claimed in claim 1, wherein the compensating springs exerta force on the front conducting element which is higher than a resultantof a compressive force exerted by the compression springs, in adirection of thrust.
 3. The switch as claimed in claim 1, wherein themoving equipment comprises a housing shaped as an asymmetric lozenge foraccommodating the compression springs, the compensating springs' housingbeing located on a same side as a most pointed corner of the asymmetriclozenge.
 4. The switch as claimed in claim 2, wherein the movingequipment comprises a housing shaped as an asymmetric lozenge foraccommodating the compression springs, the compensating springs' housingbeing located on a same side as a most pointed corner of the asymmetriclozenge.